Monday, 26 May 2014

How do you dry your washing in the summer?

Using the sun to dry your washing saves carbon emissions and £s
Do you use the tumble dryer to dry your washing even when it is warm and sunny? About half of households who have tumble dryers use them all year round, regardless of the weather. On average tumble dryers are used about 5 times per week, consuming 1.5 kWh each time. Over a year that costs around £55 and generates about 200 kg CO2. However many households use the tumble dryer a lot less or not at all in the summer, saving £s and carbon emissions [1].

No garden?

If you haven't got a suitable place outside then you can dry indoors - just hang the washing on a clothes horse or similar and open the windows in that room to make sure it gets lots of ventilation. In fact this works well in winter too, especially when the weather is dry and a bit windy, regardless of the temperature. So if you haven't got a tumble dryer at all you can use a clothes horse instead all year round.

Why shouldn't we dry our clothes over the radiators?

It is best not to dry clothes on radiators through the house in winter. Think how heavy those clothes are when wet compared to dry. That could be 4 litres of water in a load of washing - more than double the moisture you already have in a smallish home at 50% humidity at 20C. With only normal ventilation you will probably get condensation on your walls* so you must arrange for extra ventilation. In winter time that means losing valuable heat so it is best to keep the loss to one room rather than the whole house.

[1] Household Electricity Survey (DECC/Defra) based on data collected 2010/2011

* Here is my calculation,
  • Volume of home 5x8x5m = 200 m3.
  • Density of air is 1.2 kg/m3. 200*1.2 = 240 kg air.
  • Saturation point at 20C is 15.3 g water/kg air so saturation would be 240*0.0153 = 3.7 kg water
  • 50% humidity is half that. 3.7/2 = 1.8 kg water.
  • Adding 4 kg water to that takes it to 5.8 kg - way over the saturation point.

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